To:
Ted Lemon <mellon@nominum.com>
Cc:
dnsop@cafax.se
From:
Iljitsch van Beijnum <iljitsch@muada.com>
Date:
Wed, 12 Nov 2003 15:55:48 -0600
In-Reply-To:
<00E0551A-154E-11D8-879F-000A95D9C74C@nominum.com>
Sender:
owner-dnsop@cafax.se
Subject:
Re: DNS discovery
On 12-nov-03, at 14:22, Ted Lemon wrote: >> Reading RFC 2462 will clear that confusion right up. There is an >> explicit bit in router advertisements that tells hosts whether they >> should use a stateful mechanism > The stateful vs. stateless bit refers to address configuration in the > sense of getting an IP address for the node, not getting an IP address > to which to send DNS requests. When the stateful bit is set, you are > supposed to use some stateful address configuration mechanism to get > an IP address to use when communicating on the network. This is from RFC 2461, [ADDRCONF] refers to RFC 2462: 4.2. Router Advertisement Message Format Routers send out Router Advertisement message periodically, or in response to a Router Solicitation. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cur Hop Limit |M|O| Reserved | Router Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reachable Time | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Retrans Timer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options ... +-+-+-+-+-+-+-+-+-+-+-+- [...] M 1-bit "Managed address configuration" flag. When set, hosts use the administered (stateful) protocol for address autoconfiguration in addition to any addresses autoconfigured using stateless address autoconfiguration. The use of this flag is described in [ADDRCONF]. O 1-bit "Other stateful configuration" flag. When set, hosts use the administered (stateful) protocol for autoconfiguration of other (non-address) information. The use of this flag is described in [ADDRCONF]. > Your error may be in thinking that DHCPv6 is always stateful, and > perhaps in not understanding what stateful means Whether or not DHCPv6 is stateful doesn't make a lot of difference with regard to the problem we're facing. If we assume that hosts will be using router advertisements for autoconfiguration, then adding DHCP for DNS configuration is exactly that: adding another protocol. This is bad because there is now an additional mechanism that can fail and there is additional delay in configuring. Now obviously doing this using a heavy version of DHCP is worse than doing this using a light version of DHCP, but the fundamental problem is the same in both cases. The only reason I use the words stateful and stateless during this discussion is because this is what's in the RFCs. While I can relate to the slippery slope and implementing certain functionality just once arguments, I strongly believe that pragmatic operational arguments (not having an additional protocol on the wire) should carry the most weight in this very particular case. > I've heard you repeat several times that the stateless bit in the > router advertisement can be used to say which mechanism to use, but > that is completely wrong, I beg to differ. I believe the above excerpt from RFC 2461 proves my case. #---------------------------------------------------------------------- # To unsubscribe, send a message to <dnsop-request@cafax.se>.